Phase Interactions Between Place Cells During Movement

Abstract

A model is described of phase interactions between “place” cells during movement. While mean firing phases - during walking- are “narrowly” distributed near the positive peak of the dentate theta [Fox et al, 1986], individual cells shift their phase as a function of place. [Burges et al, 1994]. Phase shifts in place cells have been seen as having their origin in similar shifts made at an earlier time and stage in the firing of entorhinal cells [Burges et al 1994]. Phase shifts might instead arise from associative interactions between place cells in what might be seen as a system of coupled oscillators. A gating function has been associated with the theta rhythm. Entorhinal inputs can only excite place (and granule) cells during a critical period which is centred around the transition from the positive to the negative peak of theta. Place cells activated during this period will tend to “pull” the activity of neighbouring cells towards a phase close to the middle of theta causing a phase shift that matches the shift of activity across CA3.